#12522: GHC 8.0.1 hangs, looping forever in type-checker -------------------------------------+------------------------------------- Reporter: clinton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I'm not sure if this is a bug or hanging the compiler is expected here. This was the minimal example that causes GHC to hang: {{{#!hs {-# LANGUAGE TypeFamilyDependencies #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE AllowAmbiguousTypes #-} main = return $ f (Just 'c') data D1 x data D2 type family TF x = t | t -> x type instance TF (D1 x, a) = Maybe (TF (x, a)) type instance TF (D2, ()) = Char class C p where f :: TF (x, a) -> () }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12522 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler